A semiconductor quantum well (QW) can be broadly classified as Type 1 (electron and hole wave functions overlap substantially) and Type 2 (electron and hole wave functions are substantially non-overlapping). Either type of QW relies upon decay of (free) electrons into (vacant) holes and thus upon overlap of the electron and hole wavefunctions near the recombination region so that a Type 2 QW structure will generally have a much smaller optical gain or associated electron-hole current than does a Type I QW structure. A semiconductor material such as InAs has an attractive band gap in the mid-infrared region, but materials such as AlSb/InAs in a conventional configuration appear to have only Type II band edge lineups. This precludes use of InAs, in a conventional QW configuration, from being used to produce, or to detect, light of mid-infrared wavelengths.
What is needed is an approach for converting a Type II QW material in to Type I QW material. Preferably, this approach should be flexible and should provide a spectrum of emission wavelengths in a selected wavelength band, such as a mid-infrared band. Preferably, this approach should work with a variety of choices of column III and column V semiconductor materials and with a continuum of geometric parameters associated with the QW wells. Preferably, this approach should allow use of the converted material for detection of the presence of light and/or for production of light in a specified wavelength band.